You're 100% correct that allowing more housing will not fix things overnight - it'll take time.

"The best time to plant a tree was 20 years ago. The second best time is now."

I don't think collusion is easy in a market with so many landlords. Here's an article about Denver prices dipping a few years back due to - you guessed it - lots of supply:

https://www.curbed.com/2017/1/25/14342828/denver-rents-affor...